非人灵长类绒猴视觉运动高级皮层MT区对不同运动信息的群体细胞反应和功能构筑

Motion perception is qualitatively invariant across different objects and forms, namely, the same motion information can be conveyed by many different physical carriers. All physical motion information consists of motion signals of direction, speed and axis. In contrast, all physiological vision motion is initiated on the retina as sequential retinotopic activations representing a series of discrete locations of a moving object in space and time (motion trajectory) and is conveyed by neuronal firings of action potentials. Using motion stimuli of full-field visual noises or random dots, our recent studies at the population and single-cell levels demonstrated that the motion trajectory was processed as direction signal only at low speed but as motion-axis signal at high speed by both direction- and orientation-selective neurons in V1 and V2 of macaque and cat early visual cortices. The transition speed for direction-selective neurons was much higher than that for orientation-selective neurons. Furthermore, a spatio-temporal energy model was able to reproduce all the data recorded, suggesting that motion trajectory on the retina at both low and high speeds is linearly processed by the spatio-temporal receptive fields of direction- and orientation-selective neurons in the early visual cortices of high mammalians. In non-human primates, Middle Temporal Visual Area (MT) is the motion processing centre, which receiving feed-forward neuronal projections from V1 and V2, thus, how the direction-, orientation- and velocity-selective neurons in MT encode motion direction, speed and axis remains elusive. We hypothesize that MT neurons will bear similar neural mechanisms as their projection neurons in V1 and V2 but with much high transition speeds. To test this hypothesis, we will investigate population responses and functional organizations of direction-, orientation-, and velocity-selective neurons for processing direction, speed and axis of motion in the MT of new-world monkey common marmoset, using drifting full-field random dot motion stimuli and intrinsic optical imaging along with electrophysiological multi-units recordings. A physiological constrained spatio-temporal energy model will be employed to simulate the population responses. Together, the proposed study will reveal whether MT neurons encode motion direction at low speed but axis of motion at high speed with much higher transition speeds than those in early visual cortices. The results and findings will demonstrate that depending on motion speed, the combined processing of motion direction and axis by neurons with orthogonal direction and orientation preferences may serve as a fundamental principle of visual motion processing in earlier and higher visual areas of primates.

运动视觉是灵长类动物最重要的视觉功能之一。物理学运动都包含运动方向，速率和轴向信息，而视觉运动则起始于发生在视网膜对应视野上神经元的连续激活，是运动轨迹信息。我们前期在猕猴和家猫早期V1和V2视皮层上的研究工作表明，视网膜上的连续激活在低速时被视皮层方向和方位选择性神经元当作运动方向信息编码，而在高速时则被另一群最优方向和方位分别与低速时垂直的神经元当作运动轴向信息编码。方向和方位神经元对随机光点运动的编码没有本质区别，只是反转速率的高低不同。非人灵长类高级视觉运动皮层MT区接受V1和V2的上行前馈投射，那么MT区方向、方位和速度选择性神经元又是如何编码运动方向、速率和运动轨迹的呢？利用在体内源性光学成像和群体细胞电生理记录并结合计算机模拟，我们将研究和记录绒猴MT区方向、方位和速度选择性神经元对不同运动速率下的随机光点刺激的群体细胞反应和皮层功能构筑，力图揭示视觉运动最基础的神经机制。

运动视觉是灵长类动物最重要的视觉功能之一。物理学运动都包含运动方向，速率和轴向信息，而视觉运动则起始于发生在视网膜对应视野上神经元的连续激活，是运动轨迹信息。我们前期在猕猴和家猫早期V1和V2视皮层上的研究工作表明，视网膜上的连续激活在低速时被视皮层方向和方位选择性神经元当作运动方向信息编码，而在高速时则被另一群最优方向和方位分别与低速时垂直的神经元当作运动轴向信息编码。方向和方位神经元对随机光点运动的编码没有本质区别，只是反转速率的高低不同。非人灵长类高级视觉运动皮层MT区接受V1和V2的上行前馈投射，那么MT、MST区方向、方位和速度选择性神经元又是如何编码运动方向、速率和运动轨迹的呢？本项目结合内源光学成像、电生理、计算机建模仿真，并初步尝试了双光子成像手段，在单细胞和群体细胞水平记录和直接对比研究了猴V1、MT、MST脑区不同神经元对不同运动速率下的随机光点视觉运动刺激的神经元反应和皮层功能构筑，并探索了不同脑区编码和处理运动轴向信息的反转速率的差异，研究结果将有助于揭示视觉运动最基础的神经机制。